Thermostatic device



Sept. 24, 1935. E. BLETZ ET AL THERMOSTATIC DEVICE Filed Aug. 25, 1933Ilu- INVENTORS d www Y zw M f@ 6 T Zn/ .T J WSY wma de FZ //WWNESSES:

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THERMOSTATIC DEVICE Edward Bletz, Lexington, and Lewis J. Greenawalt,Mansfield, Ohio, assignors to Westinghouse Electric & ManufacturingCompany, East Pittsburgh, Pa., a corporation of Penn- SylvaniaApplication August z5, 193s, serial No. 686,758

claims. (o1. 20o-iss) Our invention relates to thermostatic devices andit has particularrelation to temperatureresponsive switches of the typein which a snapacting disk of bimetallic construction is utilized 5 toeffect a quick-make-and-break action.

In the construction of thermostats of the type shown in PatentNo.1,448,240, which issued March 13, 1923, to J. A. Spencer, in which asnapacting disc in the form of a non-developable sheet of two metalshaving different thermal coeiiicients is utilized, it has become almostuniversal practice to support the disc by suitable means engaging itscenter instead of its perimeter, and to mount the circuit-closingmembers actuated thereby near the perimeter instead of at the disccenter.

Contact members so mounted are thus caused to move in an arcuate paththrough a distance which is somewhat less than the axial travel of therim of the actuating disc. This particular arrangement of parts is thussubject to the disadvantage of requiring an appreciable amount of playor lost motion in the contact member mountings in order to allow themembers to be self-aligning with the stationary contacts with which theyare disposed to engage when occupying one limiting position of theirarcuate path of travel. A further disadvantage results from the factthat the magnitude of contact movement, in this construction, cannot bemade as great as that of the travel of the rim of the disc, since thecontact members must, of necessity, be mounted at some intermediateradius which is less than that of the disc rim.

Our invention is directed to an improved form of construction forthermostatic devices of the type under consideration which overcomes the-disadvantages named and which possesses additional advantages to beparticularized hereinafter.

Generally stated, the object of our invention is to provide asnap-acting-disc thermostat in which the movable contact members areactuated in a straight-line path of travel through a distance equal tothe axial movement of the disc rim.

More specifically, an object of our invention is to provide a form ofconstruction which eliminates the usual tilting of the contact membersas the bimetal disc snaps from one position to the other and which takesfull advantage of the disc movement.

Another object of our invention is to improve the self-aligningcharacteristics of the contact members in such a manner that thenecessary play in contact mounting may be substantially reduced.

A further object of'our invention is to increase the speed of motion andmagnitude of the contact separation in'thermostatic devices of the 5type under consideration.

In practicing our invention, we provide an auxiliary ring member uponwhich the movable contact members of the thermostatic switch aremounted, which ring member is supported from l0 the outer edge or rim ofthe snap-acting disc at a plurality of peripherally spaced points. 'I'hearcuate. movements of the disc rim are thereby converted into straightline or axial movements of the contact-carrying ring, which in magnitude15 are equal to the axial travel of the disc rim.

Our invention itself will best be understood from the followingdescription of specific embodiments thereof when taken in conjunctionwith the accompanying drawing in which: 20

Figure 1 is a plan view of a thermostatic switch constructed inaccordance with one embodiment of our invention in which the auxiliarycontactcarrying ring is disposed intermediate the snapacting disc andthe switch base; 25

Fig. 2 is a sectional view taken on the line II--II of Fig. 1, showingthe device of Fig. 1 in its opened-contact position;

Fig. 3 is' a similar section view illustrating the device of Fig. 1 inits closed-contact position; 30

Fig. 4 is a plan view of a thermostatic switch constructed in accordancewith a second embodiment of our invention in which the auxiliarycontact-'carrying ring is disposed to surround the snap-acting disc; and35 Figs. 5 and 6 are section views 'taken on the line V-V of Fig. 4illustrating the switch in its openedand closed-contact positionsrespectively.

Referring to the drawing, and particularly to 40 the first three guresthereof, the base or supporting member of the switch is shown generallyat I0, and is preferably composed of two sheets of metal. An internallythreaded sleeve I2 is snugly tted in a hole in the center of the base 45member and accommodates a threaded stud I4 which carries at one endthereof a flange I5 against which the snap-acting bimetallic disc l1comprised by the switch is suitably held by means `shown in the form ofa collar or nut I8. 50

Insulating material 20, which may be in the form of a sheet of mica., isattached to the base member I0 and upon it are mounted the stationarycontact members 22 to 25, inclusive. Disposed in cooperative relationwith the stationary 55 or iiat position, and the shoulders members are aplurality oi movable members 2l. Connections with an external circuit,which the switch is to control, are made through suitable terminal posts(not shown) which may be attached to the two stationary members 22 and2|, respectively. When, as shown in Fig. 3, the movable members 2l arebiased into engagement `with the stationary members, a circuit iscompleted between members 22 and 25, while, when the movable contactmembers 2t are biased out of engagement trom the stationary members,this circuit is interrupted at a plurality ot diiIerent points.

Instead oi' mounting the movable members 2t directly on the bimetallicdisc I1, as has been the prior practice, we provide an auxiliary ring2l, which is preferably cut from suitable sheet metal, upon which ringthe contact members 2l are insulatedly mounted. As illustrated in Figs 2and and 3, washers Il of insulating material may be utilised to separatethe body oi' each contact member from the ring material through whichthe stud portion of the contact extends to make a riveted connectionwith a washer I I.

The ring 2l is supported from the rim oi' snapacting disc I1 at aplurality oi peripherally spaced points by means of studs u, each ofwhich is riveted at one end in a suitable hole 34 in the ring andprovided at the other end with a slot I in which the edge of disc il isdisposed to nt. The radial clearance between the edge o! the disc andthe lower portion oi the stud slots is made sumcient to accommodate theincreased diameter of the disc when it snaps through the centralcomprised by the slots ll may be so tapered that there is practically nolost motion in an axial direction between the disc rim and thecooperating studs 33.

To maintain a proper alignment ot the contactcarrying ring 2l withrespect to the stationary contact members carried by base it, aplurality of screws Il may be inserted into suitable holes 4I in thebase member in a manner that they protrude through circular recesses uin the contactcarrying ring 2l. I! desired, the length oi these stopscrews 4l may be made such that the heads thereof serve to limit theoutward travel oi' the disc l1 by contacting the ring 2l in the mannershown in Fig. 2.

In the operation oi' the thermostatic switch constructed in accordancewith the embodiment of our invention which has just been described, asuitable change in the temperature to which disc i1 is subjected causesit to preliminarily distort and to then abruptly snap over to theopposite cupped position. Thus, when the switch occupies theopen-contact position illustrated in Fig. 2, a proper temperaturevariation will cause it to snap to the position shown in Fig. 3, themovement of the disc rim being transmitted to the contact-carrying ring2l, which moves to the right in a straight line or axial path, therebybiasing the movable contact members 26 into engagement with thestationary members supported by switch base Il. In a similar manner,when the switch is in the closed-contact position shown in Fig. 3, theoccurrence of a proper variation in temperature will cause the disc ilto move into the position of Fig. 2, thereby rapidly separating thecontact members 2t from the cooperating stationary members.

It will thus be evident that the magnitude of contact-member movement isequal to the axial travel ot the rim of the bimetallic disc i1 and thatthe arcuate path oi disc movement is converted into straight linemotion, which is highly preferable in that it reduces the amount oi playor lost motion in the mountings of the stationary contact membersnecessary to render them selialigning upon engagement with thestationary members.

The explanation thus far has assumed in effect a non-adjustablethermostat, that is, one in which the bimetal disc Il is positioned at afixed distance from the supporting base l0. When it is desired to changethe temperature-response characteristics oi the thermostat, this may bedone by moving the disc support toward or away from the base. In thedevice shown, such movement may be effected by turning the threaded studIl by means oi.' an adjusting knob (not shown) or other suitable means.When, as shown, the travel-limiting screws 40 are so arranged that theyrestrain disc movement, in the outward or opened-contact positiondirection, by engaging the contact-carrying ring 28, the outwardrestraint is imparted to the disc rim and hence is exerted on the samediameter as is the closedposition restraint provided by engagement oicontact members 26 with the stationary members carried by base lli. Wehave i'ound that such equal restraining diameters tend to allow thetemperature differential of the thermostat to remain constant fordifferent adjustments.

It will be seen that the construction of our invention just explaineddoes not appreciably increase the overall diameter oi' the thermostaticswitch, although it does somewhat raise the axial dimensions of thedevice assemblage. In the majority of applications, it will be foundthat this moderate increase in switch thickness is not particularlyobjectionable. However, in the event that minimum thickness must beretained, the advantages afforded by our invention may still be realizedthrough the utilization o! the construction shown in Figs. 4, 5, and 6which illustrate a thermostat built up in accordance with a secondembodiment oi our invention.

The switch shown in these figures is fundamentally the same as thatshown and described in connection with Figs. 1, 2, and 3, it comprisinga base member I0 through which the stud Il extends to support at one endthereof the bimetallic disc I1. Stationary contact members 22 to 2l',inclusive, are mounted upon insulating material carried by the basemember and are disposed to be engaged by the movable contact members 26,which are actuated by the disc l1.

These movable contact members 26 are carried by a ring assemblagecomprising two cooperating portions 50 and 52 which are suitablydisposed to encircle the bimetal disc Il. On the inner periphery of eachring portion an oir-set is made in such manner that there is formed anannular groove 54 in which the rim of disc Il nts in the manner shown.The mechanical connection of ring assemblage 50--52 with the disc is,therefore. equivalent to that of ring 28 which is eilected through themedium o! studs J3.

To maintain the ring assemblage Bil-J2 in proper alignment with respectto the stationary contact members carried by switch base IU', screwmembers 40' may be utilized. These members may serve the additionalpurpose of restricting the outward movement oi the disc to apredetermined limit.

It will be seen that the operation oi' the second embodiment of ourinvention, in which the contact-carrying ring is disposed to surroundthe snap-acting disc. is identical with that of the first describedembodiment in which the contactcarrying ring is mounted between the discand the switch base, the movable contact members being moved in straightlines through a distance which is equal to the axial travel of the discrim.

It will be observed that the second form of construction just describedin no way increases the axial dimensions of the thermostatic switch towhich it is applied, although it does somewhat increase the diameter ofthe switch assemblage.

Although we have shown and described certain specific embodiments of ourinvention, we are fully aware that many modifications thereof arepossible. Our invention, therefore, is not to be restricted exceptinsofar as is necessitated by the prior art and by the scope of theappended claims.

We claim as our invention:

1. In a temperature-responsive switch, the combination of a base,contact members insulatedly fixed thereon, a stud extending through saidbase, a snap-acting bimetallic disc centrally mounted at one end of saidstud, a ring member supported from the rim of said disc at a pluralityof peripherally-spaced points, contact members mounted upon said ringmember and adapted to cooperatively engage said first-mentioned contactmembers, and means adapted to directly act upon said ring member forrestricting the distance which said member may be moved by said discaway from the switch base.

2. Temperature-controlled apparatus comprising, in combination, a basemember, separated contact members insulatedly mounted upon said basemember, a snap-acting thermostatic disc, a mechanical connection betweenthe center of the disc and the base member, an auxiliary membersupported from the rim of said disc, contact members mounted upon saidauxiliary member and adapted to electrically connect with saidfirstmentioned contact members, and meas adapted to directly act uponsaid auxiliary member for restricting the distance which said member maybe moved by said disc away from said base member.

3. A temperature-responsive switch comprising a base, contact membersfixed thereon, a stud extending through said base, a snap-actingbimetallic disc centrally mounted at one end of said stud, means foradjusting the distance from the base at which said stud maintains thedisc center to thereby adjust the temperature-response characteristicsof the switch, an auxiliary member supported from the rim of said discat a plurality of peripherally-spaced points, contact members mountedupon said auxiliary member and adapted to cooperatively engage saidfirstmentioned contact members, and means adapted to directly act uponsaid auxiliary member for restricting the distance which said member maybe moved by said disc away from the switch base, the effect of saidrestraint being to maintain subst'antially constant thetemperature-differential of the switch for differing adjustments in thesaid response characteristics thereof.

4. A temperature-responsive switch comprising a base, contact membersfixed thereon, a stud extending through said base, a snap-actingbimetallic disc centrally mounted at one end of said stud, means foradjusting the distance from the base at which said stud maintains thedisc center to thereby adjust the temperatureresponse characteristics ofthe switch, an auxiliary member adapted for disposition intermediate thedisc and the base member, means for supporting said auxiliary memberfrom the rim of the disc at a plurality of peripherally-spaced points,contact members mounted upon said auxiliary member and adapted tocooperatively engage said first-mentioned contact members, and meansadapted to directly act upon said auxiliary member for restricting thedistance which said member may be moved by said disc away from theswitch base, the effect of said restraint being to maintainsubstantially constant the temperature-differential of the switch fordiffering adjustments in the said response characteristics thereof.

5. A temperature-responsive switch comprising a base, contact membersinsuiatedly fixed thereon, a stud extending through said base, asnapacting bimetallic disc centrally mounted at one end of said stud,means for adjusting the distance from the base at which said studmaintains the disc center to thereby adjust the temperatureresponsecharacteristics of the switch, an auxiliary member adapted to surroundthe disc, means for supporting said auxiliary member from the rim of thedisc at a plurality of points, contact members mounted upon saidauxiliary member and adapted to cooperatively engage saidfirst-mentioned contact members, and means adapted to directly act uponsaid auxiliary member for restricting the distance which said member maybe moved by said disc away from the switch base, the effect of saidrestraint being to maintain substantially constant thetemperaturediierential of the switch for differing adjustments in thesaid response characteristics thereof.

EDWARD BLETZ. LEWIS J. GREENAWALT.

